Laminated superrefractory article



Mar. 13, 1923.k 1,448,684

M. F. BEECHER ET AL T IUAIIAIEID SUPERREFRACTORY ARTICLE Filed Apr. 8, 192,1

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dhttt MILTN E. BEECHER A MAGDGNLB C. BOZ, 0F WORCESTER, MASSACHUSETTS,

i' DE' WQRCESTER, MASSACHUSETTS, A CQRPE LAMENATED SUPERREFRA'EY ARTECLE;

Application led April 8, 1921. Serial No. 459,738.

To all whom it may concern:

Be it known that we, MILTON l?. BEEQHER and MACDONALD C. Booze, citizens of the United States of America, residing at lflorcesfr perrefractory Articles, of which the following is a full, clear, and exact specification.

Our inventionrelates to the composition.

of a super-refractory article, and 'specilically of one having a laminated structure.

lt is readily apparent that refractory articles which are subjected to various chemical and physical reactions at high temperatures .will withstand such conditions if the parts exposed to them are protected or are themselves sufficiently resistant. rlhis re sistance has been effected in' several ways, such as bycovering the refractory structure with a coating of refractory Acement which is hardened and forms a protective layer over the surfaces treated, or by making the entire structure of suiiciently refractory material. An intermediate course has also been proposed by which the ire brick or other refractory shapes are composed of la refractory material on one side which decreases in amount toward the interior and opposite side, being progressively replaced by fire eleg.

oatings of refractory cement over lire brick structures are of necessity subjected to more severe heat treatment than the re bric-k and tend to spall and crack off when in use. lt is, moreover, expensive to manufacture the entire refractory from magnesia, and therefore inadvisable unless made necessary by other considerations. Furthermore, the proposed method of making laminated bricks is not applicable with materials which react to form non-refractory products. For example, magnesia, in either the amorphous or crystalline form, is extremely resistant to hi h temperatures under basic conditions but 1t cannot be satisfactoril teria s such as tire clay, for at elevated' temperatures 1t will flux with the tire clay formi ing an easily fused silicate. lt cannot therefore be used as a cement or as a surface coat/lng in Contact with such materials Vwhen very high temperatures are to be employed. lt is accorduigly an object of our inventlon to provide a laminated -article having a facing of su er-refractory material with a suitable an less expensive support, in which any ingredient capable of reacting with the facing material detrimentally is separated therefrom by va neutral intermediate layer.1

lt .is a further object of our invention to provide a laminated refractory article in which the composition of each layer is such that any reaction between it and an adjacent layer will form a refractory product and in which the layers Will cohere to form an integral structure. f

Another object of this invention is to provide a refractory article which has a magnesia facing with a refractory ylire clay backing, which will withstand extremelyl high temperatures andl will not warp or crack to any serious extent.

employed in contact with acid ma Other objects of our invention will be readily apparent in the following disclosure and claims. v f

ln accordance with our invention, we provide such an article with a facing layer composed of a super-refractory material, united by a bond capable of resisting high ternperatures, For example, one may employ preshrunk magnesia las the refractory and bond it with finely divided magnesia or zirconia. To provide a support for the facing, we may utilize any material having sufficient strength, such as fire clay. lf 'the support `contains an ingredient which reacts detrimentally with the facing material, it may be separated therefrom by an intermediate layer, integrally united with both the facing and the backing,`which is made upv of ingredients neutral to those of the facing layer. 'lhis inner layer, herein termed neutral, may be composed of materials less Y refractory than the facing, but they should Een react with the ingredients of the facing only to form a refractory product, if at all. For this purpose, refractory substances suchas alumina or preferably crystalline alumina may be used and bonded with any suitable material, but if less refractory than the main constituents, they shouldy be used in relatively small amount. For this bond, we may use an aluminous or vitrifiable clay, preferably low in free silica, such as one of the ball clay type. ln the case of magnesia and' aluminal being used, any reaction between them will result in the formation of a refractory spinel, and make a more intimate union between the layers.

llt may be preferable that the magnesia and alumina layers comprise the entire refractory article and if so it may be fired and put into service in this form,and backed up by the fire bricks of the furnace or other construction to which it may be a plied. lt is, however, ordinarily to be pre erred that the backing be provided with-a layer of a less expensive material and of similar composition to that of the remainder of the construction in which it is to be employed, which is most commonly lire brick. ln such cases, therefore, a third layer iS intimately joined to the second or intermediate layer already mentioned, while still in the green or unfired condition. This third layer is composed of materials which will unite but not seriously react with the ingredients of the second layer and which will be relatively inexpensive, such as fire clay or fire clay grog bonded with fire clay.

ln the manufacture of such a refractory article it is necessary that, beside consideration of the physical and chemical properties of the constituents, and their relationship, proper attention should be given to the relative coelioients of expansion and shrinkage of each layer during the drying and firing, and when in subsequent use. These factors should be. previously determined, and the l. composition of each layer adjusted so that the resultant effect upon the laminated structure of physical .and chemical changes will not disrupt the layers or the joints between them. This may be done by testing such mixtures individually, and proportioning the relative amounts of refractory and bonding materials-in each, so that the mixtures to be used will expand and contract alike when joined together into a laminated.structurc and subjected to the various conditions of driving, firing and using the finished article. Reference being had to the drawing` we ,have there illustrated in cross sectional view a three layer laminatedrefractory fire brick comprising a facing 1 of super-refractory mrial, an lntermedlate layer 2 and a fire anse clay backing 3. As a specific example of the compositions which may be used for making this type of brick, the following burnt iire clay grog, l0 lto 16 mesh.

35% burnt lire clay grog, 16 mesh and finer.

20% Mississippi ball clay.

10% kaolin.

Water is added to each mixture until sufficient plasticity is obtained for convenient molding.

ln the manufacture of a standard lire brick of this composition, we prepare a. plastic mixture of electrically fused or preshrunk magnesia, nely ground magnesia and zirconia, and water. A layer ofv this mixture is placed in the ordinary brick mold to the desired thickness, the free surface being left rough and moist.` A second mixture is then prepared, of granular crystalline alumina, the clay bond and Water, which is spread over the iirst layer` in the mold and forced against it sufficiently to make the two layers cohere intimately. lf, :1s-mentioned above. the layers of magnesia and alumina should be thick, the mold may be filled with them and the brickl thus molded carried through the drying and firing operations from this point. Otherwise, a third layer is applied upon the second. composed of crushed lire clay grog, lire clay and water, with which the mold is filled. The free surface of the brick is then finished in the usual manner and the brick may be pressed, if this is desired. The brick thus formed is then removed from the mold, allowed to dry thoroughly and fired according to the usual ceramic practice to a sufiic-ient temperature to set the bonds used and to harden the whole into a firm unitary structure throughout. The product thus obtained may be used and set up in the same fashion as the ordinary fire brick.

yao

Fire bricks or other refractory articles v as a whole, results.

high temperatures, and resist the chemical 4action of slags and other destructive matestrongly reactive substances are used in the same'refractory article, there is no danger4 of luxing. A considerable economy is also effected by making articles in accordance with my invention, for all super-refractory materials are moreexpensive than those of lower melting points which may thus be employed.

it is to be noted that while finely ground zirconia., as well as' finely ground magnesia,

was employed as the bonding agent in thel example given, either one of'these materials alone may be used as the bond with satisfactory results.. lt will also be apparent that various other changes may be made in the combinations and compositions referred -to without departing from the scope of our in vention, and also that numerous modifications a-nd adaptations may be made in the application of it to particular conditions, but 4such changes and adaptations are to be considered as included by this specification and the following claims.

Having thus described our invention,what we claim as new and desire to secure by Letters Patent is:

l.' A laminated refractory article having a facing of bonded refractory material, a reinforcing backing layer of'ceramic material which is reactive with an ingredient of the fac-ing, anda neutral intermediate layer intimately joined to and separating the facing and backing layers..

2. A laminated refractory article having a super-refractory facing comprising magnesia, a refractory ceramic hacking support therefor, and an intermediate layer composed of such material that any reaction between .it and the ingredients of .the facing shall form a refractory product.

' 3. A laminated refractory article having a facing containing highly/.refractory material, which may flux with fire clay, a backing layer of fire clay. and an intermediate neutral refractory layer intimately joined to said facing and backing.

' 4. A laminated refractoryarticle having a facing, containing preshrunk vmagnesia grains united by a bond, which is intimately joined with a reinforcing backing, comprising a layer adjacent said facing composed substantially of refractory material which is neutral towardmagnesia.'

5. A laminated refractory article having a super-refractory facing containing magnesia which isv intimately united witha reinforcing backing, comprising a layer containing alumina ladjacent said facing.

6. A laminated refractory article having a facing of bonded preshrunk magnesia which is intimately unitedwitli a backing comprising a layer of ceramic bonded crystalline alumina adjacent said facing.

v7. A laminated refractory article compris- .ing a, plurality of layers intimately united together, .the facing consisting of bonded reshrunk magnesia granules and the bac ing containing burned fire clay.

8. A laminated refractory article having a facing containing magnesia, a backing layer composed substantially of fire clay, and an intermediate layer which is relatively neutral to and intimately joined with each of said facing and backing layers.

9. A laminated refractory article having a facing of bonded magnesia, a backing layer containing fire clay, and an intermediate layer composed substantially of alumina, intimately joined to each of said facing and backin layers.

l0. a facing of bonded crystallized magnesia,

a backing layer of fire clay, and an intermediate layer of ceramic bonded crystalline alumina intimately joined to said facing and backing.

11. In a laminated refractory article, a facing of preshrunk magnesia and a bond therefor containing nely divided magnesia, said facing being intimately joined to a backing comprising a layer of material which may react with magnesia to form a refractory compound.

l2. A laminated refractory article in which the surface layer contains crystalline magnesia bonded with finely divided magnesia intimately joined to a backing, comprising a laye-r of bonded crystalline alumina adjacent said surface layer, and a layer consisting substantially of-fire clay.

13. A laminated refractory article having a facing of bonded crystalline magnesia and zirconia, and a reinforcing neutral backing intimatelyA joined thereto.

14. Alaminated refractorylarticle having a facing,r of bonded magnesia and zirconia, intimately joined to a reinforcing backing, comprising a layer containing alumina which is adjacent said surface layer.

15. Alaminated refractory article having a facing containing bonded preshrunk magnesia, finely divided magnesia and zirconia, intimately joined to a'layer of crystalline alumina, and a vitriiied ceramic bond therelaminated refractory article having l loo a i 1,44a,ase

for, and a backing united Awith said layer ing of ingredients which are neutral toward` composed substantlally 'of fire` clay and fire but unite integrally with the backing, and 10 clay grog. are capable of uniting with the magnesia to 16. A laminated refractory article comprisform a `saper-refractory roduct.

5 ing a'facing layer, thermajor portion of Signed 'at Worcester, r assachusetts, this which is magnesia, a ceramic backing layer 7th dayof Ari] 1921. substantially free from magnesia, and an in- LTON F. BEECHER. termediate body joining sald layers consist- 4 MACDONALD C. BOOZE. 

